Monday. I think I'm going to give up on the missing 2.5 weeks worth of reading. Asked JC members to contribute to reports. Yesterday was April Fool's day, so maybe some interesting papers today.
1203.6654
The probability distribution for non-Gaussianity estimators constructed from the CMB trispectrum
Smith, Kamionkowski
Trispectrum for cosmology probe. PDF of standard tau_nl amplitude estimator of the CMB trispectrum is highly non-Guassian, for both tau_nl=0 (Gaussian) and !=0 cases. Strong dependence of variance on tau_nl.
1203.6685
Binary disruption by massive black holes: hypervelocity stars, S stars, and tidal disruption events
Bromley, Kenyon, Geller, Brown
SMBH growth from ingestion of one of the binaries: one of them bound to SMBH, the other produces a single HVS. After a cluster of bound stars forms, orbital diffusion allows the BH to accrete stars by tidal disruption at a rate comparable to the capture rate. Implied binary disruption rate: 1e-3 to -5, in MW, from HVS and S star clusters. Over 10 Gyr, BH growth becomes large.
1203.6698
Unconventional cosmology
Brandenberger
Two cosmological paradigms (alternative to current inflationary scenario): (1) "matter bounce", a non-singular bouncing cosmology with a matter-dominated phase of contraction. (2) "emergent" scenario, which can be implemented in the context of "string gas cosmology". All lead to an approximately scale-invariant spectrum of cosmological perturbations.
1203.6701
Rethinking the Paleoproterozoic great oxidation event: a biological perspective
Grula
How Earth's surface became oxygenated (organic carbon burial, hydrogen escape to space, and changes in the redox state of volcanic gases), offer a more biologically-based hypothesis. Great oxidation event (GOE) ~2.4 Gyr ago: cyanobacteria expansion produced increasing flux of O2. Long delay between appearance of cyanobacteria and oxygenation of the atmosphere expected. During Archean, CH4 oxidation was a major O2 sink; GOE explained to a significant extent by a large decline in the methanogen population and corresponding CH4 flux (partial oxygenation of the surface ocean responsible). Aerobic methanotroph population established, further contributing to the large reduction in the CH4 flux to the atmosphere. Reduction in the CH4 flux lowered the CH4 oxidation sink for O2 at about the same time the metamorphic and volcanic gas sinks for O2 also declined. As the O2 source increased from an expanding population of cyanobacteria -- triggered by a burst of continent formation (2.7-2.4 Gyr ago), the atmosphere flipped and became permanently oxygenated.
1203.6724
The growth index of matter perturbations and modified gravity
Basilakos, Pouri
Constrain growth index gamma from 2dFGRS, SDSS-LRG, VVDS and WiggleZ, with z dependence; gamma=0.602 pm 0.055 for LCDM, assuming it's constant. Doesn't match the gamma_DGB value of 11/16 (measured gamma: 0.503).
1203.6760
Observational constraints on dark energy with a fast varying equation of state
De Felice, Nesseris, Tsujikawa
Monotonically increasing or decreasing w, as well as with extremum. Use SNIa, CMB, and BAO. Akaike information criterion shows that these models are not favored over the LCDM model.
1203.6813
Using deuterated H3+ and other molecular species to understand the formation of stars and planets
van der Tak
H3+ ion plays a key role in the chemistry of dense interstellar gas clouds where SF happens. Low temperatures and high extinctions of such clouds make direct observations of H3+ impossible, but lead to large abundances of H2D+ and D2H+ which are very useful probes of early stages of star and planet formation. Rotational line emission towards SF regions show that the strong deuteration of H3+ is the result of near-complete molecular depletion of CNO-bearing molecules onto grain surfaces, which quickly disappears as cores warms up after stars have formed. In the warmer parts of interstellar gas colds, H3+ transfers its proton to other neutrals such as CO and N2, leading to a rich ionic chemistry. The abundances of such species are useful traces of physical conditions such add the radiation field and the electron fraction. Recent observations of HF line emission toward the Orion Bar imply a high electron fraction, and we suggest that observations of OH+ and H2O+ emission may be used to probe the electron density in the nuclei of external galaxies.
1203.6815
The magnetic fields of hot subdwarf stars
Landstreet, Bagnulo, Fossati, Jordan, O'Toole
No strong evidence of magnetic field in any sdB or sdO star, despite earlier, contradicting reports.
1203.6828
Cosmology based on f(R) gravity admits 1eV sterile Neutrinos
Motohashi, Starobinsky, Yokoyama
As the title says.
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